The sinoatrial (SA) node controls regular and synchronized contractions among cardiac muscles in the heart. The SA node is a group of specialized cells located in the upper right atrium of the heart that functions as the normal pacemaker of the heart, generating electrical pulses that propagate through an electrical conduction system to various regions of the heart to facilitate the pumping function of the chambers of the heart. Typically, a healthy heart beats at a frequency of 60-100 beats per minute. The heart is in a normal sinus rhythm when the SA node paces the heart normally. The heart is arrhythmic if the heart's electrical activity becomes uncoordinated or irregular.
An arrhythmia involving a slow heart rhythm may be classified as bradycardia, and an arrhythmia involving a fast heart rhythm may be classified as tachycardia. Tachycardia can have its origin in either the atria or the ventricles. Cardiac rhythm management (CRM) systems may be used to treat the arrhythmic conditions of the heart. CRM systems can be configured to discriminate among different types of arrhythmias including supraventricular tachycardia (SVT), ventricular tachyarrhythmia (VT) and ventricular fibrillation (YF), and deliver antiarrhythmic therapy to the heart to interrupt the arrhythmia.
According to a known technique for classifying arrhythmias, a physician programs a programmable parameter of a CRM system to an initial value. The CRM system generally continues to deliver therapies based on the initial value without any intervention of the physician typically until the patient visits the physician during a device checkup. If the initially programmed value of the programmable parameter is not suitable for the patient, the CRM system can erroneously detect or classify cardiac events. For example, the CRM system may detect an arrhythmic episode, misclassify the arrhythmic episode as VT instead of SVT, and incorrectly deliver a therapy for the detected VT. Similarly, for example, the CRM system may detect an arrhythmic episode, misclassify the arrhythmic episode as SVT instead of VT, and incorrectly withheld a therapy for the detected SVT.